Computer system and input device thereof

ABSTRACT

A computer system including an electronic device and an input device is disclosed. The electronic device includes a touch display area and a control unit. The input device includes a plurality of positioning structures and a grounding piece. The positioning structures are electrically connected to the grounding piece. When the input device is disposed on the touch display area of the electronic device, the control unit detects positions of the positioning structures on the touch display area, calculates a coverage area covered by the input device on the touch display area according to the positions, and determines a range of a display area of the touch display area according to the coverage area.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationsserial No. 108106572, filed on Feb. 26, 2019. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of specification.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a computer system, especially, to a computersystem with an input device.

Description of the Related Art

In general, a notebook or tablet computer usually equips with only onescreen, and a virtual keyboard displayed on the screen for informationinput. However, when the virtual keyboard displayed on the smallerscreen such as on a tablet, it occupies part of the display area of thescreen and caused inconvenient while using.

BRIEF SUMMARY OF THE INVENTION

According to the first aspect of the disclosure, a computer systemincluding an electronic device and an input device is disclosed. Theelectronic device includes a touch display area and a control unit. Theinput device includes a plurality of positioning structures and agrounding piece. The positioning structures are electrically connectedto the grounding piece. When the input device is disposed on the touchdisplay area of the electronic device, the control unit detectspositions of the positioning structures on the touch display area,calculates a coverage area covered by the input device on the touchdisplay area according to the positions, and determines a range of adisplay area of the touch display area according to the coverage area.

According to the second aspect of the disclosure, an input deviceapplied in an electronic device is disclosed. The input device includesa casing, an input assembly, and a plurality of positioning structures.The casing includes a grounding piece. A wireless transmission unit isdisposed in the casing. The input assembly is disposed on the casing.The positioning structures are disposed at a side of the casing oppositeto the input assembly, protruded from the casing, and electricallyconnected to the grounding piece.

From the above detailed description of the specific embodiments, it isobvious that the positioning structures of the input device areelectrically connected to the grounding piece of the input device,thereby, the problem of poor recognition ability caused by the floatingeffect of the positioning structure is improved. When the input deviceis placed on the touch display device, the change of capacitance on thetouch sensing layer caused by the improved positioning structures isrelatively stable, so that the control unit in the touch display deviceaccurately determines the position of the positioning structure on thetouch display device. Therefore, when the input device is close to thetouch display device, the control unit can determine the position wherethe input device is placed by the positioning structure.

In addition, the input device can be disposed on a specific position ofthe touch display device by the fixing structures located thereon toprevent the input device being moved relative to the touch displaydevice when the user uses the touch display device or the input device.Furthermore, the user can also place the input device on a specificposition of the touch display device as his required, so as to improvethe convenience of the computer system.

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a computer system in an assembled stateaccording to an embodiment.

FIG. 2 is a perspective view of an input device according to anembodiment.

FIG. 3 is a cross-sectional view of the structure shown in FIG. 1 alongline 3-3.

FIG. 4A is a bottom view of the structure shown in FIG. 2.

FIG. 4B is a perspective view of a positioning structure according to anembodiment.

FIG. 4C is a perspective view showing a positioning structure accordingto another embodiment.

FIG. 5 is a flow chart showing the operation method of the computersystem according to an embodiment.

FIG. 6A is a top view of a display device according to an embodiment.

FIG. 6B is a partial structural view of a computer system in anassembled state according to an embodiment.

FIG. 7 is a partial structural top view of another computer systemaccording to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Spatially relative terms such as “below”, “underneath”, “under”,“above,” “top”, and the like, are used herein to facilitate describingthe relationship of one element or feature to another element or featurein the figure. The spatially relative terms, in addition to theorientations depicted in the figures, further encompass otherorientations of the device as it is used or manipulated. That is to say,when the orientation of the device is different from the figures (90degrees rotation or in other orientations), the spatial relative termsused in this document can also be interpreted accordingly.

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a perspective view of acomputer system in an assembled state according to an embodiment of thepresent disclosure. FIG. 2 is a perspective view of an input deviceaccording to an embodiment of the present disclosure.

As shown in FIG. 1 and FIG. 3, the computer system 1 includes an inputdevice 12 and an electronic device 15. The electronic device 15 includesa first body 10 and a second body 11 pivotally connected to each other.In this embodiment, the first body 10 and the second body 11 are touchdisplay devices, such as a capacitive touch display device. In anembodiment, the first body 10 includes a touch display area 100, awireless transmission unit 102, and a control unit 104. The touchdisplay area 100 has a display function and a touch sensing function. Inother embodiments, any suitable device can be applied to the body. Inthis embodiment, the computer system 1 is a notebook computer, which isnot limited thereto.

As shown in FIG. 1 and FIG. 2, the computer system 1 also includes theinput device 12 (see FIG. 1). The input device 12 includes a pluralityof positioning structures and a plurality of fixing structures. Theinput device 12 is placed on the touch display area 100 of the firstbody 10 and partially cover the touch display area 100 of the first body10. As shown in FIG. 2, in the present embodiment, the number of thepositioning structures is four, that is, the positioning structures 14a, 14 b, 14 c, and 14 d, but the number of the positioning structures isnot limited thereto. The positioning structures 14 c and 14 d as shownin FIG. 4A are not shown in the perspective of FIG. 2. In the presentembodiment, the number of the fixing structures is four, that is thefixing structures 16 a, 16 b, 16 c, and 16 d, but the number of thefixing structure is not limited thereto. The fixing structure 16 c asshown in FIG. 4A is not shown in the perspective of FIG. 2.

In some embodiments, the positioning structures 14 a, 14 b, 14 c, and 14d are conductive rubbers containing conductive material.

In some embodiments, the fixing structures 16 a, 16 b, 16 c, and 16 dare any structures configured to fix the input device 12 to the firstbody 10. For example, the fixing structures 16 a, 16 b, 16 c, and 16 dare attractive elements. In an embodiment, the material of the fixingstructures 16 a, 16 b, 16 c, and 16 d include a magnetic material (suchas a magnet) or a metal material, but which is not limited thereto.

Please refer to FIG. 3. FIG. 3 is a cross-sectional view of thestructure shown in FIG. 1 along line 3-3. In an embodiment, the touchdisplay area 100 of the first body 10 includes a liquid crystal display(LCD), which is not limited herein. In other embodiment, the touchdisplay area 100 is an organic light-emitting diode (OLED) display.

In this embodiment, the first body 10 of the touch display area 100includes a capacitive sensing element. The capacitive sensing componentis configured to determine whether a conductor is present on the firstbody 10 to generate a touch sensing signal for the touch display area100. The capacitive sensing element includes at least one of anelectrode or a wire. When the conductor is close to the touch displayarea 100 of the first body 10, a capacitance is formed between theconductor and the electrode/wire of the touch display area 100. Thecontrol unit 104 determines whether a conductor is present on the touchdisplay area 100 by detecting a change of capacitance at eachelectrode/wire.

In FIG. 3, the input device 12 includes a casing 120, an input assembly128, a first circuit board 126, a wireless transmission unit 122, aplurality of positioning structures 14 a, 14 b, 14 c, 14 d, and aplurality of fixing structures 16 a, 16 b, 16 c, 16 d, and a powersupply 137. The input assembly 128 is disposed in the casing 120. Insome embodiments, the casing 120 of the input device 12 is used as thegrounding piece.

In the embodiment, the input assembly 128 includes a keycap 121, aconductive elastic element 123, and a lifting guide element 125. Theconductive elastic element 123 is disposed on the first circuit board126. The lifting guide element 125 of the input assembly 128 is locatedbetween the keycap 121 and the first circuit board 126, such that thekeycap 121 moves relative to the first circuit board 126. The liftingguide element 125 of the input assembly 128 in the embodiment is ascissor support structure, which is not limited thereto. When the keycap121 of the input assembly 128 is pressed, the lifting guide element 125changes from an open state to an overlapped state. Next, the keycap 121gradually approaches the first circuit board 126 to contact theconductive elastic element 123 to transfer the pressure from the keycap121 to the first circuit board 126, causing the first circuit board 126to be pressurized and electrically conducted to pass the signal.

In the embodiment, the wireless transmission unit 122 includes a secondcircuit board 127, a transfer chip 129, and an antenna 135. The secondcircuit board 127 of the wireless transmission unit 122 is disposed on aside of the first circuit board 126 opposite to the input assembly 128,and electrically connected to the first circuit board 126. The transferchip 129 and the antenna 135 are respectively disposed on the secondcircuit board 127. The wireless transmission unit 122 of the inputdevice 12 is configured to transmit signals to the wireless transmissionunit 102 of the first body 10 as shown in FIG. 1, for transmitting userinstructions from the input device 12 to the first body 10. In thisembodiment, the wireless transmission units 102 and 122 are Bluetoothcommunication units, which is not limited thereto.

In an embodiment, the power supply 137 provides power to the firstcircuit board 126 and the wireless transmission unit 122. The wirelesstransmission unit 122 of the input device 12 and the power supply 137are electrically connected to the grounding piece 124. The first circuitboard 126 of the input device 12 is electrically connected to thegrounding piece 124 by the wireless transmission unit 122 and the powersupply 137.

In FIG. 3, the positioning structures 14 a, 14 b are disposed on thecasing 120 of the input device 12 and protruding from the casing 120. Inaddition, the positioning structures 14 a, 14 b are disposed on a sideof the input device 12 opposite to the input assembly 128. In otherwords, the positioning structures 14 a, 14 b protrude from the side ofthe input device 12 opposite to the input assembly 128. In theembodiment, the positioning structure 14 a protrudes from the surface140 of the input device 12, which is not limited thereto.

In an embodiment, the positioning structures 14 a, 14 are electricallyconnected to the grounding piece 124 of the input device 12, whereby thefloating effect of the positioning structures 14 a, 14 b is reduced.When the input device 12 is placed on the touch display area 100 of thefirst body 10, the change of capacitance on the touch display area 100caused by the positioning structures 14 a, 14 b is relatively stable, sothat the control unit 104 of the first body 10 accurately identifies theposition of the positioning structures 14 a, 14 b on the first body 10and reduces the probability of identifying errors of the control unit104. Therefore, when the input device 12 is adjacent to the first body10, the control unit 104 identifies the position of the input device 12placed on the touch display area 100 by the positioning structures 14 a,14 b.

Please refer to FIG. 4A. FIG. 4A is a bottom view of the structure shownin FIG. 2. As shown in FIG. 4A, the positioning structures 14 a, 14 b,14 c, and 14 d are adjacent to the outer edge 120 p of the casing 120 asshown in FIG. 3. Specifically, the bottom surface 120 b of the casing120 has two opposite long sides 131 and 132, and two opposite shortsides 133 and 134. The positioning structures 14 a, 14 b, 14 c and 14 dare disposed on the bottom surface 120 b of the casing 120. Thepositioning structures 14 a and 14 b are respectively located on twoopposite sides of the long side 131. The positioning structures 14 c and14 d are respectively located on two opposite sides of the long side132. The positioning structures 14 a and 14 c are respectively locatedon two opposite sides of the short side 133. The positioning structures14 b and 14 d are respectively located on two opposite sides of theshort side 134.

As shown in FIG. 4B, the vertical projection of the positioningstructure 14 a on the bottom surface 120 b of the casing 120 as shown inFIG. 4A is rectangular. In the embodiment, the extension direction ofthe long sides 131 and 132 of the bottom surface 120 b as described inFIG. 4A is defined as direction X, and the extension direction of theshort sides 133 and 134 of the bottom surface 120 b is defined asdirection Y. In the view of FIG. 4B, the width W1 of the positioningstructure 14 a along the direction X is greater than its width W2 alongthe direction Y, which is not limited thereto. In an embodiment, thewidth W1 of the positioning structure 14 a is about 10 mm, and the widthW2 is about 3 mm.

As shown in FIG. 4C, the vertical projection of the positioningstructure 14 a on the bottom surface 120 b of the casing 120 as shown inFIG. 4A is circular, which is not limited thereto. In an embodiment, thediameter R of the positioning structure 14 a is about 8 mm. In someembodiments, the vertical projection of the positioning structure 14 aon the bottom surface 120 b of the casing 120 is elliptical or anysuitable shape.

Please refer to FIG. 3 and FIG. 4A. As shown in FIG. 3, the fixingstructures 16 a, 16 b are disposed on the casing 120 of the input device12 and protruding from the casing 120. In addition, the fixingstructures 16 a, 16 b are disposed on a side of the input device 12opposite to the input assembly 128. In FIG. 4A, the fixing structures 16a, 16 b, 16 c, and 16 d are adjacent to the outer edge 120 p of thecasing 120. The fixing structures 16 a and 16 b are located on twoopposite sides of the long side 131, and are respectively adjacent tothe positioning structures 14 a and 14 b. The fixing structures 16 c and16 d are located on two opposite sides of the long side 132 and arerespectively adjacent to the positioning structures 14 c and 14 d. Thefixing structures 16 a and 16 c are located on two opposite sides of theshort side 133. The fixing structures 16 b and 16 d are located at twoopposite sides of the short side 134.

In FIG. 3, the first body 10 further includes a plurality of fixingcomponents, such as fixing components 106 a, 106 b, 106 c, 106 d, 106 e,106 f, 106 g, and 106 h, that showed in FIG. 6A. In the embodiment, thefixing components 106 a, 106 b of the first body 10 are configured toattract the fixing devices 16 a and 16 b of the input device 12 todetachably fix the input device 12 to the first body 10. In theembodiment, the fixing components 106 a, 106 b are made of attractivematerial. Therefore, the material of the fixing components 106 a, 106 bis magnetic material or metal material, which is not limited thereto. Inpractical applications, the fixing components 106 a, 106 b are anystructures to mutually fix the input device 12 and the first body 10.

Thereby, the input device 12 is combined to a specific position on thefirst body 10 by the fixing structures 16 a and 16 b located thereon toimprove the strength of the overall structure of the computer system 1,moreover, it prevents the input device 12 being moved relative to thefirst body 10 when the user uses the first body 10 or the input device12. Furthermore, the user is allowed to place the input device 12 at aspecific position on the first body 10 as needed, so as to improve theconvenience of the computer system 1.

In FIG. 3, the positioning structure 14 a and the fixing structure 16 arespectively have a surface 140 and a surface 160 away from the casing120 of the input device 12. The distance D1 between the surface 140 ofthe positioning structure 14 a and the casing 120 is substantially thesame as the distance D2 between the surface 160 of the fixing structure16 a and the casing 120. Thereby, when the input device 12 is placed onthe first body 10, it is ensured that the positioning structure 14 a onthe input device 12 contacts the touch display area 100, so that theinput device 12 is coupled to the first body 10.

In FIG. 5, the method 1000 disclosed herein is illustrated and describedas a series of steps or events, but it should be understood that theorder of such steps or events are drawn is not construed in a limitingsense. For example, some steps may occur in different orders orconcurrently with other steps or events, except for in the orderillustrated or described herein. In addition, the implementation of oneor more aspects or embodiments described herein may not require all ofthe illustrated operations. Furthermore, one or more of the stepsdepicted herein may be implemented in one or more separate steps and/orstages. Specifically, the operation method 1000 includes steps 1001 to1006.

In step 1001, turn on the computer system shown in FIG. 1.

Please refer to FIG. 3, in step 1002, collect the touch sensinginformation on the touch display area 100 by the control unit 104 in thefirst body 10.

In step 1003, determine whether the positioning structure is detected atthe preset position. When the positioning structure is detected at thepreset position, step 1004 is performed. In contrast, when thepositioning structure is not detected at the preset position, step 1005is performed. Please refer to FIG. 6A. FIG. 6A is a top view of adisplay device according to an embodiment of the present disclosure. Thefixing components 106 a to 106 h in the first body 10 is disposed onboth sides of the touch display area 100. Specifically, when the inputdevice 12 as shown in FIG. 4A is placed on the first body 10 as shown inFIG. 6A, the fixing structures 16 a, 16 b, 16 c, and 16 d on the inputdevice 12 are corresponding to the fixing components 106 a, 106 b, 106c, and 106 d on the first body 10, to detachably fix the input device 12to the lower side of the touch display area 100 of the first body 10,see FIG. 1.

Alternatively, when the input device 12 as shown in FIG. 4A is placed onthe first body 10 as shown in FIG. 6A, the fixing structures 16 a, 16 b,16 c and 16 d on the input device 12 are corresponding to the fixingcomponents 106 e, 106 f, 106 g and 106 h located in the first body 10,to detachably fix the input device 12 to the fixing component 106 e, 106f, 106 g and 106 h in the first body 10, see FIG. 6B.

Furthermore, when the input device 12 is detachably fixed to the firstbody 10, the positioning structures 14 a, 14 b, 14 c, and 14 d locatedon the input device 12 as shown in FIG. 4A change the capacitance valueof a specific position in the touch display area 100 as shown in FIG. 3.

In an embodiment, since the positioning structures 14 a, 14 b, 14 c, and14 d shown in FIG. 4A are respectively adjacent to the fixing structures16 a, 16 b, 16 c, and 16 d located on the input device 12, when thefixing structure 16 a, 16 b, 16 c, and 16 d are respectively fixed tothe fixing components 106 a, 106 b, 106 c, and 106 d as shown in FIG.6A, the positioning structures 14 a, 14 b, 14 c, and 14 d respectivelygenerate touch sensing signals on the touch display area 100 at presetpositions P1, P2, P3, and P4 adjacent to of the fixed components 106 a,106 b, 106 c, and 106 d. The control unit 104 detects changes ofcapacitance at the preset positions P1, P2, P3, and P4 to determine thatthe input device 12 is placed on the lower side of the touch displayarea 100, and forms a corresponding coverage area C1 on the first body10.

Similarly, when the control unit 104 detects changes of capacitance inpreset positions P5, P6, P7, and P8 as shown in FIG. 6A, it determinesthat the input device 12 is placed on the upper side of the touchdisplay area 100, and forms a corresponding coverage area C2 on thefirst body 10.

Please refer to FIG. 7. The computer system 5 shown in FIG. 7 includes adisplay device, positioning structures, fixing structures (not shown inFIG. 7 by this view), fixing components (not shown in FIG. 7 by thisview), and an input device 52. The structure and function of thesecomponents and the connection relationship between the components aresubstantially the same as those of the computer system 1 shown in FIG. 1and FIG. 2, the related descriptions may be referred to, and details arenot described herein again. The difference between this embodiment andthe embodiments shown in FIG. 1 and FIG. 2 is that, in the embodiment,the computer system 5 replaces the input device 52 shown in FIG. 1 andFIG. 2. The input device 52 completely covers the touch display area 100of the first body 10 as shown in FIG. 6A.

When the input device 52 is detachably fixed to the first body 10, thepositioning structures on the input device 52 respectively generatetouch sensing signals at the preset positions P1, P2, P7, and P8 of thetouch display area 100. The preset positions P1, P2, P7, and P8 areadjacent to the fixed components 106 a, 106 b, 106 g, and 106 hrespectively. The control unit 104 detects changes of capacitance at thepreset positions P1, P2, P7, and P8 to determine whether the inputdevice 52 completely covers the touch display area 100 of the first body10 as shown in FIG. 6A.

In the present embodiment, the positioning structures 14 a, 14 b, 14 c,and 14 d as shown in FIG. 4A only appear in the preset positions P1, P2,P3, P4, P5, P6, P7 and P8, as shown in FIG. 6A, therefore, whendetecting the positioning structures 14 a, 14 b, 14 c, and 14 d, thecontrol unit 104 only needs to detect the preset positions P1, P2, P3,P4, P5, P6, P7, and P8 to confirm whether the input device is placed onthe first body 10, which improves the processing speed of the controlunit 104.

In step 1004, perform a touch initialization correction operation todelete the coverage area. Specifically, the control unit 104 as shown inFIG. 3 calculates the coverage area of the input device 12 at the touchdisplay area 100 based on the positions on the first body 10respectively corresponding to the positioning structures 14 a, 14 b, 14c, and then the control unit 104 determines the range of the displayarea of the touch display area 100 based on the coverage area of theinput device 12.

For example, in FIG. 1, the control unit 104 determines that the inputdevice 12 is placed on the lower side of the touch display area 100. Inan embodiment, the control unit 104 calculates the coverage area C1covered by the input device 12 on the touch display area 100 (see FIG.6A), and determines the range of the display area 100 a of the touchdisplay area 100 based on the coverage area C1 covered by the inputdevice 12 on the touch display area 100. The display area 100 a of thetouch display area 100 is an area of the touch display area 100 withoutbeing covered by the input device 12. Therefore, the control unit 104limits the first body 10 to display images in the display area 100 a.

Similarly, in FIG. 6B, when the control unit 104 determines that theinput device 12 is placed on the upper side of the touch display area100, the control unit 104 calculates the coverage area C2 covered by theinput device 12 on the touch display area 100 (see FIG. 6A), anddetermines the range of the display area 100 b of the touch display area100 based on the coverage area C2 covered by the input device 12 on thetouch display area 100. The display area 100 b of the touch display area100 is an area of the touch display area 100 without being covered bythe input device 12, therefore, the control unit 104 limits the firstbody 10 to display images in the display area 100 a.

However, in FIG. 7, when the control unit 104 determines that the inputdevice 52 completely covers the touch display area 100 of the first body10 as shown in FIG. 6A, the control unit 104 is configured to controlthe touch display area 100 not to display any image.

In step 1005, perform a touch initialization correction of the wholearea. When the control unit 104 of the first body 10 does not detect anyone of the positioning structures 14 a, 14 b, 14 c or 14 d of the inputdevice 12 on the preset positions P1, P2, P3, P4, P5, P6, P7 or P8 asshown in FIG. 6A, the control unit 104 determines that the input device12 is not placed on the first body 10. At this time, the control unit104 controls the entire touch display area 100 of the first body 10 tobe the touch display area.

In step 1006, the touch display mode is activated in a specific areadetermined by the control unit 104, or the touch display mode of thefirst body 10 is turned off.

From the above detailed description of the specific embodiments, it isobvious that the positioning structures of the input device areelectrically connected to the grounding piece of the input device,thereby the problem of poor recognition ability caused by the floatingeffect of the positioning structure is improved. When the input deviceis placed on the touch display device, the change of capacitance on thetouch sensing layer caused by the improved positioning structures isrelatively stable, so that the control unit in the touch display deviceaccurately determines the position of the positioning structure on thetouch display device. Therefore, when the input device is close to thetouch display device, the control unit can determines the position wherethe input device is placed by the positioning structure.

In addition, the input device can be disposed on a specific position ofthe touch display device by the fixing structures located thereon toprevent the input device to be moved relative to the touch displaydevice when the user uses the touch display device or the input device.Furthermore, the user can also place the input device on a specificposition of the touch display device as his required, so as to improvethe convenience of the computer system.

Although the present invention has been described in considerable detailwith reference to certain preferred embodiments thereof, the disclosureis not for limiting the scope. Persons having ordinary skill in the artmay make various modifications and changes without departing from thescope. Therefore, the scope of the appended claims should not be limitedto the description of the preferred embodiments described above.

What is claimed is:
 1. An input device, applied in an electronic device,comprising: a casing, including a top plate, a bottom plate, and agrounding piece between the top and bottom plates; an input assembly,disposed on the top plate of the casing; and a plurality of positioningstructures made of a conductive rubber, in direct physical contact witha bottom surface of the grounding piece and protruding downwardly fromthe grounding piece and penetrating through the bottom plate of thecasing to an outside of the casing, wherein when viewed in a crosssection, at least one of the positioning structures has a curved bottomsurface; and a fixing structure comprising a magnetic material andprotruding downwardly from a bottom surface of the bottom plate of thecasing, wherein when viewed in the cross section, the fixing structurehas a flat bottom surface level with a bottommost position of the curvedbottom surface of the at least one of the positioning structures.
 2. Theinput device according to claim 1, further comprising a first circuitboard, disposed in the casing and above and electrically connected tothe grounding piece.
 3. The input device according to claim 2, whereinthe positioning structures are respectively disposed at two oppositesides of an outer edge adjacent to the input device, and electricallyconnected to the first circuit board.
 4. The input device according toclaim 1, wherein the grounding piece extends along an upper surface ofthe bottom plate of the casing and a top surface of the at least one ofthe positioning structures.
 5. The input device according to claim 1,further comprising a wireless transmission unit located in the casingand electrically connected to the grounding piece.